Stability studies of ionic liquid [EMIm][NTf₂] under short-term thermal exposure

Abstract

Ionic liquids (ILs) as new media for synthesis and as functional fluids in technical applications are still of high interest. Cooling a steel component from an annealing temperature of nearly 850 C down to room temperature in a liquid bath is a technically important process. The use of ionic liquids offers advantages avoiding film boiling of the quenching medium. However, such a high immersion temperature exceeds the thermal stability of the IL, for example such as [EMIm][NTf 2 ]. To obtain information about formation of potential toxic decomposition products, potential fragments at varied states of decomposition of [EMIm][NTf 2 ] were studied by various spectroscopic and gravimetric methods. For the first time it was possible to quantify fluorine-containing products via mass spectrometry coupled directly with thermogravimetric (TG) measurements. While chemical and spectroscopic analysis of thermally stressed ILs revealed no hints concerning changes of composition after quenching hot steel for several times, the mass-spectrometer (MS) coupled TG analysis gives information by comparing the decomposition behaviour of fresh and used ILs. A number of fragments were detected in low amounts confirming the proposed decomposition mechanism.Fig. 1 Chemical structure of [EMIm][NTf 2 ].

From Polymerizable Ionic Liquids to Poly(ionic liquid)s: Structure-Dependent Thermal, Crystalline, Conductivity, and Solution Thermoresponsive Behaviors

“…TGA thermograms (Figure S41) of representative ILM and its corresponding PIL sample, [C 18 vim]­[NTf 2 ] and P­[C 18 vim]­[NTf 2 ], showed higher thermal stabilities with degradation temperatures (∼450–480 °C) compared to those (∼300–350 °C) of ILMs/PILs with a Br – ion. Such higher thermal stability for imidazolium IL with a NTf 2 – ion was also observed by other research groups . In addition, as observed for [C 2( n =7–11) vim]­[Br], DSC cooling thermograms of [C 2( n =7–11) vim]­[NTf 2 ]­s also showed a prominent T c for each sample, which increased along with the increase of Δ H c upon increasing the length of the associated alkyl chain (Figure B and Table ).…”

Effect of Isomerism on the Liquid–Liquid Phase Behavior of Mixtures of 1-Alkyl-3-methylimidazolium Bis((trifluoromethyl)sulfonyl)amide Ionic Liquids with Heptanol

“…Furthermore, DMP shows a similar, even more pronounced behavior. In this case, the critical point of the systems could not be reached within a temperature range up to T = 450 K, an experimental limitation owing to the stability range of the neat IL up to T = 400 K . The results obtained for the mixtures with C 2 mimNTf 2 (Figure ) corroborate the observations made for the mixtures of C 4 mimNT 2 with C 7 alcohols.…”

Vapor pressure of ionic liquids at low temperatures from AC-chip-calorimetry

“…The boiling point of the quenching medium must be avoided because of the unfavorable Leidenfrost phenomenon. [40][41][42][43] Because of our reliable estimation of the boiling point for [EMIm][NTf 2 ], which exceeds twice the commonly acknowledged range of T b for typical ILs, the search for high temperature applications for common ILs can be extended significantly.…”